Embolic stroke is the nation's third leading killer for adults. Embolic stroke is also a major cause of disability. The most common cause of embolic stroke is thrombus formation in the left appendage on the atrium. In almost all atrial fibrillation (AF) patients suffering from embolic stroke, a thrombus clot forms in the appendage of the left atrium.
The primary therapy for the prevention of stroke in AF patients is the administration of oral anticoagulants. Although somewhat effective, there are numerous side effects, including bleeding and lifestyle compromises. Pharmacological therapies (such as Warfarin®) are not well tolerated by patients. The introduction of biomaterials into the left atrial appendage has resulted in the biomaterials eventually breaking down resulting in clot formation. The left atrial appendage has been removed by others via open chest and thoroscopic surgical approaches. Such a procedure is described by Johnson in U.S. Pat. No. 5,306,234 entitled “Method for Closing an Atrial Appendage.” The '234 patent discloses a method for grasping the left atrial appendage and manipulating it into position in order to sever the tissue and remove the appendage. The wound on the heart is then sewn or clamped shut.
Appriva Medical, Inc. disclosed concepts for occluding the left atrial appendage from a percutaneous endocardial approach. In U.S. Pat. No. 6,152,144 entitled “Method and Device for Left Atrial Appendage Occlusion” assigned to Appriva Medical, a device and method for isolating the left atrial appendage from the inside of the heart is disclosed. A barrier or other device is anchored in the chamber of the left atrial appendage to prevent the passage of blood into and out of the chamber and thereby prevent clot formation. However, any foreign device left in the chamber of the heart is a potential thrombosis-generating site. In addition, biomaterials are known to eventually break down and result in clotting.
Some surgeons will remove or oversew the left atrial appendage as a concomitant procedure during other cardiac surgery. This is done under general anesthesia and may result in additional trauma to the patient.
While endoscopic or percutaneous approaches reduce the invasiveness of the surgical procedure, the above-described approaches have inherent limitations. Surgical removal of the left atrial appendage is very invasive and often results in loss of atrial hormones, such as atrial natriuretic peptide (ANP), and significant bleeding. In U.S. Pat. No. 6,666,861 issued to Grabek and entitled “Atrial Remodeling Device and Method,” a method is disclosed for applying a suture lasso placed endoscopically around the left atrial appendage to isolate it from the atrium. The '861 patent describes using either wet cauterization to remove the tissue or leaving the isolated appendage in place.
Endoscopic stapling devices, suture loops tied to the base of the appendage, and clips pinching the appendage from the outside surface to the base to close the appendage are used by physicians to isolate and remove the left atrial appendage. In U.S. Pat. No. 6,488,689 issued to Kaplan and entitled “Methods and Apparatus for Transpericardial Left Atrial Appendage Closure,” a method and apparatus to close the left atrial appendage is disclosed. The '689 patent describes using a grasper and a closing loop or clip applied to the outside of the left atrial appendage. The clip is applied extending toward the chamber of the atrial appendage and extending over the outside edge of the appendage. The clips of the '689 patent are a U-shaped metal clip, having a spring tendency to hold its shape, being deformed to open while positioned to extend over the tissue, before the clip is allowed to return to its resting shape, having the tissue pinched between the ends of the clip.